The present invention relates in general to the reclamation of un-poured concrete and, more particularly, it relates to a closed system for such wastes wherein there are no unused products.
Many years ago, the construction of concrete structures was accomplished by mixing the individual ingredients -- aggregate, sand, cement, and water -- at the site, in a stationary mixer, then transferring it to a container and pouring it from the container into the forms. At the end of each day, or periodically during the day, the mixers and containers were flushed with water to prevent hardening of remnant concrete therein, the wash water and contained solids going down the nearest drain.
More recently, the stationary mixer has been replaced by the so-called "transit mix" truck, which is charged with the raw materials at a central plant, which mixes them into concrete while in transit, and discharges the product upon arrival at the site. Upon return from each delivery, each truck is flushed with water for the same reasons as stated above.
Still more recently, very large industrial plants have been constructed for the sole purpose of producing pre-cast concrete products, ranging from modest, residential-type concrete blocks to elaborate building-facing panels and structural elements. Again, every piece of equipment contacted by the wet concrete must be regularly flushed with water to prevent hardening thereof and consequent equipment breakdown.
Whether producers of concrete realized the economic value of what was being flushed down the drain, or whether they were forced to consider it by the threat of increasingly stringent water pollution laws and a lack of land-fill sites, is now moot. The fact is that attention has been paid to the problem. It is also considered that solutions proposed heretofore have been less than satisfactory, for a particular reason that will become apparent from consideration of what is deemed to be the most relevant prior art.
The following U.S. Pat. Nos. are, insofar as the present invention is concerned, quite similar, though they differ amongst themselves substantially: 2,942,731; 3,278,022; 3,596,759; and 3,695,427. All of these references are concerned with the reclamation of unpoured concrete. Generally, they disclose flushing the mixer or other equipment with water, separating from the resulting mixture sand and aggregate as separate fractions, and washing these fractions to remove cement and render them suitable for re-use. The thrust of each of these inventions is the particular means employed to separate, wash and recover the sand and the rock. There is little if any disclosure about what to do with what is left over, which is a slurry of cement and water. Two patentees disclose settling basins, and one of these suggests collection of the slurry for "disposal in any suitable manner." Another merely refers to it as "overflow."
The problem, in brief, is that under current environmental regulation conditions, there is no "suitable manner" for disposal of this slurry, whether or not it is thickened in a settling basin. It is considered likely that many concrete producers do use settling basins, and periodically clean out the collected muck and dump it "out in back."